函数结束后，PHP是否会立即释放局部变量? [英] Does PHP free local variables immediately after the function ends?

问题描述

代码可以更好地说明我的要求:

The code illustrates better what I'm asking:

function foo(){

  $var = get_huge_amount_of_data();

  return $var[0];
}


$s = foo();

// is memory freed here for the $var variable created above?

do_other_stuff(); // need memory here lol

所以我知道$ var在某个时候被释放了，但是PHP是否有效地做到了?还是我需要手动设置昂贵的变量?

So I know that $var gets freed at some point, but does PHP do it efficiently? Or do I manually need to unset expensive variables?

推荐答案

您可以在类上看到此示例，这是因为您可以捕获"释放类的析构函数中的变量:

You can see this example on a class, that's because you can "catch" freeing a variable in class' destructor:

class a {
  function __destruct(){
    echo "destructor<br>";
  }
}

function b(){ // test function
  $c=new a();
  echo 'exit from function b()<br>';
}

echo "before b()<br>";
b();
echo "after b()<br>";

die();

此脚本输出:

before b()
exit from function b()
destructor
after b()

因此现在很明显，变量在函数出口处被销毁了.

So it is now clear that variables are destroyed at function exit.

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